How variable geometry turbochargers (VGT), or variable nozzle turbochargers (VNT) work. Variable geometry turbos use vanes to alter the air flow path of the exhaust gases to maximize boost across the entire rev range. During low boost operations, the vanes create a narrow path to the exhaust turbine. As the revs increase and exhaust builds, an actuator rotates the vanes, increasing the area of the path to the turbine, and allowing for greater flow, thus increasing boost at higher RPM. Variable geometry turbochargers can make twin turbo charging systems obsolete.
One goal of a regulated turbine is to expand the usable flow rate range in practical applications while maintaining a high level of efficiency. To accomplish this, the turbine output is regulated by changing the inflow angle and inflow speed at the turbine wheel inlet. In the case of the VTG turbocharger from BorgWarner Turbo Systems this is achieved using guide vanes located in front of the turbine wheel.
When the guide vanes are in the closed position, the high circumferential components of the flow velocity and a steep enthalpy gradient lead to a high turbine output and therefore to a high charging pressure. When the guide vanes are in the fully open position, the turbine reaches its maximum flow rate and the velocity vector of the flow has a large centripetal component. The advantage of this type of output control over bypass control is that the entire exhaust mass flow is always directed through the turbine and can be converted to output. The guide vanes adjustments can be controlled by a series of different pneumatic or electrical regulators.
How variable geometry turbochargers (VGT), or variable nozzle turbochargers (VNT) work. Variable geometry turbos use vanes to alter the air flow path of the exhaust gases to maximize boost across the entire rev range. During low boost operations, the vanes create a narrow path to the exhaust turbine. As the revs increase and exhaust builds, an actuator rotates the vanes, increasing the area of the path to the turbine, and allowing for greater flow, thus increasing boost at higher RPM. Variable geometry turbochargers can make twin turbo charging systems obsolete.
One goal of a regulated turbine is to expand the usable flow rate range in practical applications while maintaining a high level of efficiency. To accomplish this, the turbine output is regulated by changing the inflow angle and inflow speed at the turbine wheel inlet. In the case of the VTG turbocharger from BorgWarner Turbo Systems this is achieved using guide vanes located in front of the turbine wheel.
When the guide vanes are in the closed position, the high circumferential components of the flow velocity and a steep enthalpy gradient lead to a high turbine output and therefore to a high charging pressure. When the guide vanes are in the fully open position, the turbine reaches its maximum flow rate and the velocity vector of the flow has a large centripetal component. The advantage of this type of output control over bypass control is that the entire exhaust mass flow is always directed through the turbine and can be converted to output. The guide vanes adjustments can be controlled by a series of different pneumatic or electrical regulators.
No comments:
Post a Comment